When initializing serial disable all interrupts as some of these may
have been enabled by a bootloader. This ensures that the NRF52
serial driver remains compatible with any bootloader version.
Make the following enhancement:
-Support serial port use without flow control
-Prevent dropped bytes by updating flow control handling
-Remove dead code
Serial port use without flow control:
In the prior implementation there was a window of time between
reloading DMA buffers after a timeout where bytes could be dropped.
This is because the uart needed to be turned off in order to flush the
bytes in the DMA buffer.
This change configures the DMA buffer to only receive one byte at a
time so there is no need to disable the uart to flush it. After each
byte is received the DMA transfer will be over so the transfer will
never be partially complete and need flushing. Since the uart is
always on it is safe to use it even without flow control.
Prevent dropped bytes by updating flow control handling:
To prevent dropped bytes due to high latency the flow control handling
of the RTS line was configured to be asserted automatically by
hardware after each byte. Once the CPU has read the byte and setup
the next receive buffer the RTS line is deasserted to the transfer can
continue. This ensure that when flow control is enabled data won't be
lost due to interrupt latency.
Remove dead code:
With the above changes there is a lot of dead code, such as the timer
handling code. This patch removes the code that is no longer used.
### Description
Arm compiler 5 builds with "short" enums and "short" wchars. This means
that C/C++ enums will be packed into the smallest power of 2 number of
bytes by the compiler and the `wchar_t` is 2 bytes. Arm compiler 6
defaults to packing enums into 4 bytes and `wchar_t` is 4 bytes.
Further, Arm Compiler 5's `-O0` (no optimizations) bulids will actually
do some amount of optimizing, similar to Arm Compiler 6's `-O1`. I have
switched the debug profile to `-O1` for maximum compatibility with our
prior behavior.
NOTE: "Compatibilize" is a word
### Pull request type
[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change
### Description
The Mbed 2 release was broken for FF_LPC546XX as it would include
the entire mbed 2 build of the LPC546XX. This PR seperates these 2
builds completely by:
* Removing non-shared extra labels from the MCU_LPC546XX target
* Moving the target implementation to a shared target directory
### Pull request type
[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change
Busy-wait before sending a charecter instead of after. If
serial_writeable has been called first, the busy-wait loop will
be skipped.
Added initialization code to ensure NRF_UARTE_EVENT_TXDRDY is
armed correctly.
Martin Kojtal
Russ Butler
Cruz Monrreal II
Bence Káposzta
Teppo Järvelin
Russ Butler
Jimmy Brisson
Senthil Ramakrishnan
Marcus Chang